Bridge construction

ABSTRACT

Viaduct construction comprised of a set of taut lengthwise cables surrounding and supporting tubular sections having internal roadway surface for vehicles. Sections, cradled in cables, stiffen the set of cables against catenary sag. Assembled sections and surrounding set of cables wrapped with high tensile strength sheeting further stiffening the assembly. Assembly received in tubular anchors supported in abutments.

United States Patent. [191 Barkdull, Jr.

[4 1 May 7,1974

[ BRIDGE CONSTRUCTION [76] Inventor: Howard L. Barkdull, Jr., 15117 Edgewater Dr., Lakewood, Ohio 44107 22 Filed: July 15, 1971 21 Appl. No.: 162,783

[52] US. Cl. 14/1, 52/224 [51] Int. Cl E0ld l/00 [58] Field of Search 14/3, 4, 5, 6, 17, 18,

[56] References Cited UNITED STATES PATENTS 2,706,498 4/1955 Upson 52/224 X 3,300,921 1/1967 Middendorf.... 52/224 X 2,716,864 9/1955 Hacker 52/224 X 3,162,709 12/1964 Davidson 52/224 X 11,407 8/1854 Baldwin 14/1 3,118,811 l1/l963 Eggink 52/224 X 3,084,481 4/1963 ,Silberkuhl 52/174 X 108,663 10/1870 White 14/3 2,347 11/1841 Rogers 14/3 1,176,994 3/1916 Spelling 14/4 1,447,257 3/1923 Lindenthal 14/17 FOREIGN PATENTS OR APPLICATIONS 642,128 6/1962 Canada 52/174 Primary Examiner-Nile C. Byers, Jr. Attorney, Agent, or Firm-Ely & Golrick [5 7] ABSTRACT Viaduct construction comprised of a set of taut lengthwise cables surrounding and supporting tubular sections having internal roadway surface for vehicles. Sections, cradled in cables, stiffen the set of cables against catenary sag. Assembled sections and surrounding set of cables wrapped with high tensile strength sheeting further stiffening the assembly. Assembly received in tubular anchors supported in abutments.

7 Claims, 2 Drawing Figures PATENTED HAY 71974 ArraP gy BRIDGE CONSTRUCTION This invention relates to improvements in bridges and like viaducts for vehicles and, more particularly, a construction affording a novel and optimum utilization of the tensile strength of steelcables and sheet, stiffened by the compressive strength of concrete and like tubing.

The relatively enon'nous tensile strength of steel cables comprised of a multitude of wires has long been used in suspension bridges. Heretofore to equalize the tensile load along the length of the transverse cables, they have been hung in the familiar catenary' curve between high intermediate suspension towers and secured in abutments at the ground or highway level on opposite sides of a waterway or ground to be spanned. To overcome the inherent elasticity and flexibility of such cables and thesystem of vertical cables by which the roadway is suspended from the main transverse cables, the roadway has been part of a stiff sub-structure, usually a truss construction of relatively rigid struts and beams. Unlessthe cable suspension system is thus ade-' quately stiffened, the suspended roadway is subject to unnerving undulations and flexings which make the bridge difficult to traverse and'such vibrations induced by traffic and transverse windloads can compound to magnitudes and frequencies which cause the bridge to fail and collapse. The increasing costs of such towers, abutments, and roadway systems have now generally limited the .use of suchsuspension bridges to long spans at sites which do not permit the use of multiple supporting pieces connected by simpler beam; arch, and truss systems which depend, at least in a major part, upon the compressive strength of the composite bridge material and do not fully utilize the tensile strength of the metals which may be used with concrete and like relatively inelastic components of composite materials; nor, as demonstrated by this invention, has optimum use been made of the compressive strength of such inelastic materials.

It is an object and advantage of this invention to make fuller utilization of the tensile and compressive strengths of conventional materials available for construction and to minimize and simplify the substructures such as abutments, piers, and roadway; the need for high and costly suspension towers is eliminated. Viaducts made according'to this invention are adapted for use as bridges spanning, water ways and chasms and as the spans of elevated highways and may be erected with a minimum of need for support or access from the area being spanned.

Other objects and advantages of this invention will be apparent from the following specification, claims, and drawings, in which:

FIG. 1 is a side view, partly diagrammatic and partly in section, of a single-span bridge made' according to this invention.

FIG. 2 is a cross-section taken alongthe line 2-'2 of FIG. 1.

Referring to the drawings, in which, for purposes of illustration, the elements are shown diagrammatically rather than in proportional dimensions, the span is supported by abutments 11. Such abutments are approached in this instance by conventional earth work ramps 12 supporting the paved highway surface Eat the grade required by the site to join with the roadway surface within the span. The abutments I] are erected on a suitably excavated bed-rock or stable sub-soil base or, if the site is a deep marsh or such that the sub-soil is unstable and too deep over bed-rock or a stable straturn, the abutments may be erected upon suitable piles or sunken mattress slabs in a conventional manner.

The abutments 11 are usually of poured reinforced concrete or similar conventional masonry work up to the level for the anchor rings 14 as hereinafter described, provision being made for the pairs of vertical steel or other high tensile strength anchor rods 15, one pair of which, 15a and 15b, is shown in FIG. 1 in each abutment. These anchor rods 15 may terminate and be secured within their respective abutments if the abutments are themselves sufficiently large and stable and- /or anchored in bed-rock. Or, as shown in FIG. 1, the anchor rods may extend downwardly for anchoring in bed-rock or in piles or suitable similar mattress slabs; if the anchor rods terminate in the abutments, their function is solely to secure the anchor rings 14 in the abutments; if, as shown, they extend below the abutments, they also function to fix and stablize the abutments as well. For relatively short spans and single lane roadways, one pair of anchor rods per abutment may be sufficient; in longer spans or for multi-Iane roadways requiring larger and longer anchor rings, a plurality of pairs of anchor rods are preferably employed. When the anchor rods terminate in the abutment or in closely adjacent bed-rock, they may be fabricated off the site as large U-bolts; in most instances, however, the legs 15a and b are straight rolled shapes extending above the anchor rings and are fabricated into a U-shaped structure on the site by a cap 15c welded or otherwise secured to the legs 15a and b.

The anchor rings 14 are large steel horizontally extending tubular members supported in the abutments 11; they may be fabricated as such off the site but are usually fabricated on the site by welding together suitable segments of rolled shapes or plates. The remote ends of the rings 14 carry heavy inner flanges l6 slotted to receive the ends of the tensile support cables 20 and provide a bearing for the cable-securing means 25 and 26, as shown in FIG. I at each abutment 11.

The span 10 extends between the anchor rings 14 and is comprised, asshown in FIG. 2, of a set of high tensile wire cables 20 circumferentially located about and supporting an inner tube 21, assembled from mating sections 22. The sections 22 are preferably of high compressive strength concrete, usually reinforced. They are most conveniently trucked to the site from an off-site fabricating plant where they may be cast with an internal integral roadway surface 23 dividing the interior of the sectioninto a lower passageway U for utility conduits and an upper and large passageway V for vehicles. As so fabricated, the reinforcing (notshown) is preferably pre-stressed to provide optimum stiffness for each section. Such off-site fabrication also conveniently allows the provision for suitable openings for ventilation, conduits for lighting, receptacle for drainage grids, and access openings from the passageway V into the passageway U and like conventional equipment (all omitted from the drawings).

The cables 20 are usually arranged in an oddnumbered set, seven in this instance, whereby, as shown, a majority of the cables in the set are located so as to cradle and support the sectional inner tubing as the structure is constructed and to locate them in the area of maximum tensile stress in the span. Though diagrammatically shown as circular in cross-section, the cables are built up from strands arranged in the conventional numbers numbers of 7, 19, etc. By so arranging a multiplicity of cables about the periphery of the inner tube, stock pre-spun and pre-formed cable may be employed, as contrasted with the more expensive on-site spun cable required in conventional suspension bridge constructions relying upon one or two main cables.

The outer surface of the sections 22 are, as shown, suitably grooved or otherwise configured to receive the cables 20 in the desired arrangement. To hold the cables 20 in this arrangement and also to support and transmit the radial compressive load of the outer strip metal sheath 30, a length of appropriately configured pre-cut and suitably reinforced concrete spacer slab 24 is inserted between each pair of cables 20. The circumferential joints between the spacer slabs 24 preferably overlap the joints between the tubular sections 22, as shown in FIG. 1.

The sheathing 30 is a wrapping of relatively thin high tensile strip steel, preferably stainless, both to utilize the great tensile strength of stainless steel and to reduce maintenance. It is under substantial tension, preferably as high as 50 percent of the yield point of the strip. By providing the span with a smooth outer surface, it minimizes wind loads, but its principal function is to impart a high radially directed compressive load on the relatively imcompressible and inelastic sections 22 and 24 of the span 10.

To construct a span as disclosed, after the abutments 11 are built up to receive the anchor rings 14 which are then locked in place by the anchor rods 15, the flanges 16 of the rings 14 are left exposed while the cables 20 are strung between the anchor rings and secured by suitable means, such as cable-securing thimbles 25, each carrying a large nut or wedging means 26 by which the tension on each cable may be progressively increased. When each of the relatively light individual cables 20 have been tensioned to substantially eliminate their catenary sags between the anchor rings, the first tubular section 22 is slid to the center of the span on the cradle provided the lower cables of the set and subsequent sections are then added to approach each of the locking rings 14. By compressing the joined sections against each other by temporary tension means extending between the end sections, the inner tube 21 stiffens and sag on the cables 20 may be progressively taken up as the tube 21 is built up. Thereafter the slabs 24 are laid in and wrapped in place as the sheath 30 is laid in tension over them. Such tension may be applied by mechanical means, but pre-heating the portions of the strip being laid spirally on the slabs and then welding the abutting edges will tension the strip and maintain it under tension during seasonal and daily temperature changes.

After the span is thus fabricated, the abutment ll may be completed to provide a tunnel entrance 31 to the span, in which case a chamber 32 is preferably formed to allow access for maintenance of the cable securing means. Ventilating openings in the sheath 30 to correspond to pre-formed matching openings in the sections 22 and slabs 24 may be made by welding a suitable frame to the exterior of the sheathing and then removing the strip within the frame.

It is to be understood that this invention is not limited to the specific embodiment disclosed, but may be modified and altered by those skilled in the art without departing from the scope of the following claims. Nor is the invention confined to vehicular bridge constructions or only to single span constructions. ln overhead highways, the spans may extend between piers replacing the abutments 11. Similar span constructions and supports may also be used for conveyor belts, pipelines, and like bulk transportation means.

What is claimed is:

1. A span construction comprising end supports, an inner tubular sub-structure having substantial compressive strength extending between said supports, a plurality of cables of relatively higher tensile strength and elasticity also extending catenarily between and supported by said end supports and bearing on the periphery of said tubular sub-structure to support the same, and means to maintain said cables under tension and reduce the catenary sags thereof between said end supports.

2. Span construction as defined in claim 1, including an outer sheathing of relatively high tensile strength around said cables, said sheathing being under tension to impart an inward radial compressive load on said cables and tubular substructure, shifting the compressive load in the upper portion of said tubular sub-structure toward the lower portion thereof and the tension load on the lower cables toward the upper cables bearing on said tubular structure.

3. A span construction as defined in claim 2 in which said tubular sub-structure is comprised of axially extending tubular sections.

4. A span construction as defined in claim 3, including spacer slab sections spacing said cables from each other and said sheathing from said inner tubular substructure.

5. A span construction as defined in claim 4, in which the joints between said slab sections overlap the joints between said tubular sections.

6. A span construction as defined in claim 5 in which the ends of said assembly of inner tubular sections, cables, spacer slab sections, and sheath are received in anchor rings, located in said end supports.

7. A span construction as defined in claim 6 in which said anchor rings extend horizontally in said end supports and include anchor bolts extending vertically in said supports to fix said anchor rings therein. 

1. A span construction comprising end supports, an inner tubular sub-structure having substantial compressive strength extending between said supports, a plurality of cables of relatively higher tensile strength and elasticity also extending catenarily between and supported by said end supports and bearing on the periphery of said tubular sub-structure to support the same, and means to maintain said cables under tension and reduce the catenary sags thereof between said end supports.
 2. Span construction as defined in claim 1, including an outer sheathing of relatively high tensile strength around said cables, said sheathing being under tension to impart an inward radial compressive load on said cables and tubular substructure, shifting the compressive load in the upper portion of said tubular sub-structure toward the lower portion thereof and the tension load on the lower cables toward the upper cables bearing on said tubular structure.
 3. A span construction as defined in claim 2 in which said tubular sub-structure is comprised of axially extending tubular sections.
 4. A span construction as defined in claim 3, including spacer slab sections spacing said cables from each other and said sheathing from said inner tubular sub-structure.
 5. A span construction as defined in claim 4, in which the joints between said slab sections overlap the joints between said tubular sections.
 6. A span construction as defined in claim 5 in which the ends of said assembly of inner tubular sections, cables, spacer slab sections, and sheath are received in anchor rings, located in said end supports.
 7. A span construction as defined in claim 6 in which said anchor rings extend horizontally in said end supports and include anchor bolts extending vertically in said supports to fix said anchor rings therein. 